Two-cycle internal-combustion engine



Nov. 28, 1950 F. M.- JONES 2,532,273

'rwo-cycua INTERNAL-COMBUSTION ENGINE Filed Dec. 24, 194': 5 Sheets-Sheet 1 INVENTOR. Fwunmcx M. Jam-:s

Nov. 28, 1950 F. M. JONES TWO-CYCLE INTERNAL- COMBUSTION ENGINE Filed Dec. 24, 1947 5 Sheets-Sheet 2 FREDERKK M. J owes zzo rzzey Nov. 28, 1950 F. M. JONES 2,532,273

TWO-CYCLE INTERNAL-COMBUSTION ENGINE Filed Dec. 24, 1947 5 Shees-S heet 3 k fly. 5 V 2 38 lb 1 INVENTOR. FEwtmck M. JONES Attorney Nov. 28, 1950 F. M. JONES TWO-CYCLE INTERNAL-COMBUSTION ENGINE 5 Sheets-Sheet 4 Filed Dec. 24, 1947 Miam Nov. 28, 1950 F. M. JONES TWO-CYCLE INTERNAL-COMBUSTION ENGINE 5 Shuts-Sheet 5 Filed Dec. 24, 1947 F eoemcx mJones Patented Nov. 28, 1950 TWO-CYCLE INTERNAL-COMBUSTION ENGINE Frederick M. Jones, Minneapolis, Minn., assignor to U.S

Thermo Control 00., Minneapolis,

Minn., a corporation of Minnesota Application December 24, 1947, Serial No. 793,589

8 Claims. 1

My invention relates to improvements in a two cycle internal combustion engine. In particular it relates to an engine of the class described having a novel means of pre-compressing the fuel charge prior to its introduction into the combustion chamber and utilizes in place of valves, internal passages within the engine, which are opened and sealed by the movement of the pistons.

In the earlier forms of two cycle engines, the fuel in the form of a compressible fluid was introduced into the crankcase of the engine and received primary compression by the downward movement of a piston during its power stroke.

After the fuel charge was compressed in the crankcase in this manner, it was permitted to travel through suitable passages into the combustion area above the piston where it was again compressed prior to combustion. The undesirable feature of this arrangement was that in order to properly lubricate the crankcase and its cooperating parts and at the same time to utilize this part of the engine as a compression chamher. it was necessary to mix a portion of lubricant with the fuel and inject the mixture into the crankcase. In this arrangement the lubricant would not always be assured of reaching the several moving surfaces in sufficient quantity to properly lubricate them and, therefore, the engine was subject to excessive wear because of poor lubrication. A further disadvantage resided in the excessive use of lubricant since a considerable portion oi this material would naturally be conveyed in small droplets with the fuel to the combustion chamber.

More recently engines of this type were designed with pre-compression chambers formed as an integral part of each cylinder and arranged beneath the piston but sealed from the crankcase, such as is shown in my Patent No. 2,417,253, granted March 11, 1947. Designs of this general nature did away with the intermingling of fuel and lubricant and involved a valveless engine. However, in order to provide for the passage of the pro-compressed fuel. numerous complicated passages had to be formed in the cylinders and pistons which naturally increased the cost of producing such an engine.

The present invention is directed to a two cycle engine wherein one cylinder is used for combustion purposes and another independent cylinder is used to pre-compress a fluid charge which may be either air or a hydrocarbon mixed with air, together with a simplied form of passage for transmittin the pro-compressed charge to the combustion cylinder. Each of the cylinders is provided with a piston that is connected to a common crankshaft and arranged in their sequence of reciprocating movement so as to provide for the correctly timed inter-passage and ignition of the fluid charges. By this arrangement one pro-compression piston will have completed or be in the act of completing its compression stroke at the moment that a combustion piston is moving to a position where a fresh charge of compressed fluid may be introduced into the combustion cylinder. To transfer the pro-compressed charge from the one cylinder to the other, a passage extends between the two cylinders. A portion of this passage includes a passage formed within the interior of the precompression piston. The piston passage originates in the upper end of the piston and terminates in a side wall where it communicates with the remainder of the passage that extends to the combustion cylinder.

As an engine of this type must necessarily include at least two combustion cylinders, and it may contain any multiple of two cylinders, an equal number of rare-compression cylinders are provided so that each combustion cylinder is served by an independent pro-compression cylinder. To simplify the arrangement of cylinders and to minimize the number of passages, the two sets of cylinders are arranged in opposing parallel lines so that they form opposite lines of cylinders extending along the top of an engine casing and form a V type engine. This arrangement also enables a simplication of the fluid inlet passage to pre-compression cylinders so that an equal quantity of fluid is received in each cylinder, and it also enables the use of a single connecting passage between the two sets of cylinders to thereby avoid the use of a multiplicity of individual passages between each pre-compression cylinder and its cooperatin combustion cylinder.

An object is to provide an engine of the type described having a plurality of combustion cylinders and a plurality of pro-compression cylinders extending from the top of an engine in a V arrangement with a single continuous passage Joining the several cylinders to deliver the precompressed charges from the pro-compression cylinders to the combustion cylinders.

Another object is to provide a two-cycle engine composed of at least two combustion pistons and a corresponding number of pumping pistons which operate in combination with the combustion pistons, a crankshaft having two crank arms disposed at an angle of 180 with respect to each other, together with means for interconnecting two non-cooperating pistons to each arm of the crankshaft so that a balanced condition is maintained between the two cooperating pairs of pistons.

Another object is to provide a two cycle engine having independent combustion and pro-compression cylinders which are laterally spaced from each other and connected by a passage, in which the timing of movement of the piston in the pre-compression cylinder is advanced with relation to the combustion cylinder piston so as to overcome the inertia of the fluid and have the same in a completely pre-compressed condition when the combustion cylinder is ready to receive the charge when the crankshaft is rotating in one direction, or to act as a pump and force the charge into the combustion cylinder when the crankshaft is rotating in an opposite direction.

Other and further objects will become apparent from the following description and claims, and in the appended drawings in which:

Fig. 1 is a front end elevation of a two cycle engine forming the present invention;

Fig. 2 -is a section taken on the lines 2-2 of Fig. 1, looking in the direction of the arrows;

Fig. 3 is a section taken on the lines 33 of Fig. 2;

Fig. 4 is a section taken on the lines 4-4 of Fig. 2 and showing a piston in its uppermost position within a cylinder;

Fig. 5 is a vertical section taken on the lines 55 of Fig. 1, showing the combustion cylinders in side elevation;

Fig. 6 is a section taken on the lines 6-6 of I Fig. 1 and shows in plan view a portion of the fuel inlet passage;

Fig. '7 is a sectional view taken on the lines 1--'! of Fig. 3 showing in plan view a pair of precompression cylinders and a pair of combustion cylinders and an inter-connecting passage therebetween;

Figs. 8 and 9 diagrammatically show the positions of opposite pairs of pistons when they are in their various extreme positions;

Figs. 10, 11, 12 and 13 show a pair of cooperating combustion and pre-compression cylinders in four different positions of their cyclic movement.

Referring now to Fig. 1, a two cycle engine indicated by the general reference numeral I4, is formed with an engine ca ing l5 which at its opposite ends as shown in Fig. 2, is provided with removable plates I 6 and I1, which respectively carry bearings l8 and I9 to support the opposite ends of a two cycle crankshaft to be described later. The engine casing I5 is provided with a plurality of ventilating fins 20 for radiating heat from the casing I5.

Extending from the upper end of casing I5 is a combustion cylinder block 22 composed of a plurality of cylinders each having a detachable cover 24. A plurality of fins 26 are provided on the cylinder block 22 for cooling purposes. Extending from one side of cylinder block 22 is an exhaust conduit 28.

Also extending from the upper surface of engine casing I5 is a pre-compression cylinder block 30 which extends angularly from the casing so as to form an inclusive angle of substantially 45 or less with relation to cylinder block 22, as will be clearly evident in Fig. 1. Cylinder block 30 is composed of a plurality of cylinders each of which is provided with a detachable 4 cover 32. Block 30 is also provided with a plurality of cooling flns 34. Extending into the upper end of cylinder block 30 is a fluid inlet conduit 36 which is adapted to be connected to a source of suitable fluid.

Referring now to Fig. '7, cylinder block 22 is composed of a plurality of cylinders 38 and 40, and while here shown as being only two cylinders, it will be understood that cylinder block 22 may be composed of a larger number of cyinders such as might constitute any multiple of two. Likewise, cylinder block 30 is composed of a pair of cylinders 42 and 44 and might be composed of any larger number, provided there are an equal number of such cylinders as there are cylinders in the block 22. The two groups of cylinders form opposing lines of cylinders which extend angularly from the top of the engine casing.

Referring now to Figs. 2 and 3, a crankshaft indicated by general reference numeral 45 is mounted within engine casing I5 and is sup- Iported for rotation on the bearings l8 and I9. Crankshaft 45 is of conventional two cycle design and provided with the arm portions 46 and 48 which are spaced from each other 180 in their cycle of rotation. On either end, the crankshaft 45 is provided with extensions 41 and 49 for connection to appropriate driven members.

Joined to each of piston arm portions 46 and 48 of crankshaft 45 by a connecting rod 5|] are a plurality of identical combustion pistons 52 and 52a, see Figs. 3, 5, 8 and 9, which are provided with the usual wrist pins 54 and piston rings 56. Pistons 52 and 5211 are of conventional design, but for further understanding, each is provided with a raised surface 58 on its upper end which at one side is formed in a sharp curve 60 and at its other side is slanted at 62. Also connected to crankshaft portions 46 and 48 by connecting rods 64 are apluralityof identical pre-compression pistons 66 and 66a, see Figs. 2, 3, 8 and 9, having the usual wrist pin connections 68, and adjacent their upper and lower extremities, the usual piston rings 10.

Referring now to Fig. 4, piston 66 is shown in cross section, it being understood that pistons 66 and 66a are identical in construction. Shown as slopingly extending from the side of one wall of the piston to a lower extremity on the other wall is a web 12 which forms a chamber 14 on the lower end of the piston which is open at its lower extremity, and which houses the wrist pin 68 that connects the piston to piston rod 64. Above web 12 and open through the upper surface of the piston 66 is a second chamber 16, which is sealed from chamber 14 by web 12. Extending downwardly from chamber 16 is a vertical passage 18 which terminates in an opening extending through the lower side wall of the piston. As shown in Figs. 2 and 4, a short web 82 extends at right angles from web 12 to the adjacent piston wall and divides opening 80 so as to provide support for web 12 and also to strengthen the piston wall on either side of opening 80.

Referring now to Fig. 7 in conjunction with Fig. 2, it will be understood that a first combustion piston 52 will be mounted in cylinder 38, and an identical piston 52a will be mounted in cylinder 40. A first pre-compression piston 66a will be mounted in cylinder 42, and an identical piston 66 will be mounted in cylinder 44. The pistons 52 and 66a of cylinders 38 and 42, as shown in Figs. 8 and 9, are connected to portion 48 of crankshaft 45 and will reciprocate in unison with each other. Similarly the pistons 52a and 86 in cylinders 40 and 44 are connected to portion 46 of crankshaft 45 and will also reciprocate in unison. Thus it follows that the pistons 52 and 66 in cylinders 38 and 44, and also the pistons 52a and 66a in cylinders 40 and 42 reciprocate in opposite directions with relation to each other and form a cooperating pair of pistons. Therefore, as will be set forth in detail hereinafter, each pro-compression cylinder cooperates with an obliquely disposed combustion cylinder and in this relationship, and particularly as shown in Figs. 3 and -13, they form a cooperating pair of cylinders.

As will be evident from an examination of Figs. 8-13, the two pistons forming a pair of cooperating pistons extend angularly with relation to each other, but they are both connected to the same crankshaft. The angle which they extend from the crankshaft has an important effect on the timing of the reciprocation of the pistons. As shown in Figs. 8 or 13, when piston 52 is at its lowest position, the head of its cooperating precompression piston 66 is spaced slightly from the top of cylinder M. Likewise, as shown in Fig. 12, when piston 66 is at the top of its compression stroke, piston 52 has not quite finished its power stroke. Actually, piston 66 is moving slightly ahead of piston 52 so that the fluid is completely compressed and its inertia overcome prior to the time that piston 52 and its cylinder is ready to receive a fresh fluid charge. This is an important feature when the engine is of a high speed type.

Referring now to Fig. 6 in conjunction with Figs. 1, 3 and 4, the fluid inlet 36 connects to a passage M in cylinder block 30 and passes ar cuately about cylinder ll to a triangularly shaped opening 8t: which extends downwardly within the cylinder block to a passage Bil. shown in Fig. 7. The downwardly extending passage 86 joins the center of passage 88 between cylinders t2 and M and extends arcuately about each of cylinders M and it as shown at at and 92. A plurality of inlet passages il l extend through the wall of cyllnder M and another plurality of passages tlli extend through the wall of cylinder M. The passages M and 96 are to provide inlet for the fluid to each of cylinders 62 and M. On their diametrically opposite sides cylinders l2 and M are provided with outlet passages 98 and Mill which join to a large common passage Hi2, which extends from the outlet sides of cylinders 42 and M in cylinder block (ill to a plurality of passages IM and I06 in the side walls of cylinders 38 and M of cylinder block 22. Cylinders 3H and til on their other sides are provided with exhaust passages Hi8 and Mil, which join a common exhaust passage l H that extends to the exhaust passage lid, shown in Fig. 1.

An engine of the type described may be used as a gasoline engine, in which case the fluid charge will be a mixture of gasoline and air, and the same is ignited by conventional spark plugs such as is shown in dotted lines in Fig. 3, and indicated by reference numeral I I4. However, the

pistons are of substantially equal size. but it should be understood that when used in a Diesel combination the pre-compression cylinders and pistons may be of larger size than the'combustion cylinders and pistons and that other variations may be made in the size of the passages.

While not specifically described, the engine would be lubricated in a conventional manner by a forced feed lubricating system not illustrated.

The operation of the engine will now be explained in detail. By referring to Figs. 2, 'l, 8 and 9, it will be apparent that a combustion piston 52 and a pre-compression piston 66a would be joined to portion 48 of the crankshaft 45 and another pair of combustion and pre-compression pistons 52a and 66 would be joined to crankshaft portion 46. In each case the relatively opposite pistons connected to a single portion of the crankshaft would operate together and in unison, as shown in Figs. 8 and 9. so that with this arrangement a combustion piston 52 in cylinder 33 will have reached the lower extremity of its reciprocating movement when a pre-compression piston 66 in cylinder 44 will be in a relatively opposite position. Likewise, a combustion piston 52a in cylinder in will cooperate in the same manner with a pre-compression piston 66a in cylinder 42. It further being understood that the respective pistons 52 and 52a in cylinders 38 and 4'0 reciprocate in opposite directions as is equally true of the pre-compression pistons 66 and 66a in cylinders t2 and 44.

Fluid, such as air or an air-gas mixture, is introduced into cylinder block 30 through the inlet it, passage ill, downwardly extending passage 86, and thence equally distributed in both directions through portions ill and 92 of the lower passage 88.

Referring now to Fig. 2, in conjunction. with Figs. 7 and ill, the pre-compression piston lit in cylinder M is at its lowermost position so that fluid in passage 88 is free to enter the several inlet openings 96 above the upper end of the piston. At the same time the combustion piston 52 in cylinder 38 is approaching its uppermost extremity and the openings Hi0 and mt on either end of passage I02 are closed.

Referring now to Fig. 11, an explosion has just occurred in cylinder 38 and has forced piston 52 to move downwardly and piston 66 to move upwardly to the extent that the inlet openings 95 in cylinder 44 are now closed by the pro-compression piston 66, but the piston has not yet reached a position where openings fill) in the cylinder wall are in communication with the opening 30 at the lower end of passage 18 in the piston. Under these conditions the fresh charge of fluid is being compressed in cylinder M.

Referring now to Fig. 12, piston 66 has reached its extreme upper position in cylinder M' and the opening at the lower extremity of the piston is now in alignment with the openings I00 and the cross passage I02, and the compressed fluid within chamber 16 is now free to flow through passage 18 and enter passage I02. However, piston 52 is still sealing the openings I06 and. therefore, the fresh fluid charge cannot yet enter cylinder 38. However, the passage )2 has suflicient capacity to hold the compressed charge. At the same time that the charge is being delivered to passage H02 it will be noted that the openings I I0 are now partially in communication with the area above piston 52 and the exhaust gases can commence to pass from the interior of cylinder 38 through the openings I I0.

Referring now to Fig. 13, piston 52 has reached its lowermost extremity and piston 66 has started to move downwardly. Under these conditions the compressed charge of fluid is free to leave passage I02 and enter the openings I06 in cylinder 38 where it contacts the curved surface 60 on the head 58 of piston 52 and is turned upwardly within cylinder 38 to aid in purging the spent gases past the slanting surface 62 of the piston head through opening IIO.

As has been previously pointed out, the two cylinder blocks are angularl disposed with relation to each other so as to form an inclusive angle of 45 or less. This arrangement causes one of the pistons forming a cooperating pair of pistons to move slightly in advance of the other piston even though the pistons are connected to opposite arms of the crankshaft. In Figs. 10-13 the crankshaft is shown as rotating in a counterclockwise direction and the pre-compression piston 66 is moving in advance of the combustion piston 52. This action'permits the piston 66 to complete its compression stroke prior to the time that piston 52 uncovers the opening I06. Thus the inertia of the charge is offset and it is in a fully compressed condition in passage I02 when piston 52 uncovers opening I06. Such an ar rangement is highly desirable if the engine is to be used for high speed operation.

If, however, the crankshaft is rotated in a clockwise direction, piston 52 moves in advance of piston 66 and in that case piston 52 will be in the position of Fig. 13 when piston 66 is in the position of Fig. 12. This permits the compressed charge to be delivered from passage 18 through passage I02 to cylinder 38 directly and at the instant that piston 52 uncovers opening I05. Rotation of the crankshaft in a clockwise direction is desirable if the engine is to be used for slow speed operation since under these conditions piston 56 is giving a direct pumping action which will give better scavanging of the burn gases in cylinder 38.

In the foregoing an explanation has been given of the operation of the combustion piston 52 in cylinder 38 and a pre-compression piston 66 in cylinder 44. It will be understood that a combustion piston 52a in cylinder 40 and a pre-compression piston 66a in cylinder 42 will be reciprocating in exactly opposite directions so that the power necessary to continue the movement of the pistons 52 and 66 in cylinders 38 and 44 as shown in Fig. 13 will be supplied by a combustion and power stroke of the similar piston 52a in cylinder 40.

Referring to Fig. 7, it will now be evident that the single passage I02 which connects the pair of pre-compression cylinders with the pair of combustion cylinders is operative to provide a common communication between the pairs of cylinders, but since the cooperating pairs of cylinders operate in cycles of 180 with relation to each other, the common passage I02 is operable to supply fluid from one pre-compression cylinder to one combustion cylinder and the other cylinders will be sealed until their respective pistons have reached the predetermined position, such as is shown in Figs. 12 and 13, where they in turn are operative to deliver fluid one to the other.

The advantages of m invention result from the simplicity of structure which reduces the number of passages within the cylinder blocks and the engine casing by utilizing the longitudinal passages through the pre-compression pistons 66 and 65a to deliver the fluid when it has reached its maximum degree of compression. Furthermore, this single common passage I02 between the two cylinder blocks simplifies the construction for delivering the fluid from the precompression portion of the engine to the combustion portion of the engine.

My invention is not restricted to the single illustration, but is defined in the terms of the appended claims.

I claim:

1. A two cycle engine, comprising an engine casing, a first pair of cylinders extending from said casing forming two combustion chambers, a second pair of cylinders extending from said casing forming two pre-compression chambers, each of said pairs of cylinders extending angularly from said casing in opposite relation to the other pair of cylinders in a manner as to form an inclusive angle which is not in excess of 45 between the respective pairs of cylinders, a crankshaft positioned in the casing, a piston in each cylinder and connected to the crankshaft in such a manner that the pistons in each pair of cylinders simultaneousl reciprocate in opposite directions, means for conducting fluid to the pair of pre-compression chambers, and a passage extending between the first and second pairs of cylinders. said passage forming a common communication between all of the cylinders for the passage of pre-compressed charges from the second pair of cylinders to the first pair of cylinders in such a manner that each combustion cylinder receives through the common passage 3, pre-compressed charge from its obliquely opposite precompression cylinder.

2. A two cycle engine, comprising an engine casing, a, first line of cylinders extending from said casing and forming a line of combustion chambers, a second line of cylinders extending from said casing in parallel relationship to the first line of cylinders and forming a line of precompression chambers, each of said lines of cylinders extending angularly from the casing in a manner as to form an inclusive angle of substantiall 45 between the lines of the cylinders, a piston in each cylinder, a crankshaft positioned in said casing and connected to each of said pistons in such a manner that the piston in one combustion chamber reciprocates in an opposite direction to the piston in the next adjacent combustion chamber and in unison with the piston situated in the substantially opposite pre-compression chamber, and a passage extending between the flrst and second lines of cylinders forming a common communication between all of the chambers forming both of said lines of cylinders whereby ,a first cylinder from either end in the line of pre-compression chambers is operable to supply fluid fuel through said passage to an obliquely opposite second cylinder in the line of combustion chambers.

3. A two cycle engine, comprising an engine casing, a first line of cylinders extending from said casing and forming a group of combustion cylinders, a second line of cylinders extending from said casing in spaced relation to the first line of cylinders and forming a group of precompression cylinders, and a passage extending between the second and first lines of cylinders forming a common communication between all of the cylinders forming both of said lines of cylinders for the passage of pre-compressed charges from the second line of cylinders to the first line of cylinders.

4. A two cycle engine, comprising an engine casing, a first line of cylinders extending from both of said lines of cylinders, said passage forming a second means of cooling the pre-compressed charges before the same enter the first named cylinders.

5. A two cycle engine, comprising a crankshaft having a pair of spaced apart crank-arms disposed at an angle of 180 with respect to each other, a working piston connected to one of said arms, a pumping piston connected to the other of said arms to normally reciprocate in a direction opposite to the working piston, a passage for I conducting pressurized fluid from the pumping piston to a point above the head of the working piston. and a pair of cylinders surrounding said pistons and connected to the opposite ends of said passage, said cylinders being disposed at an angle of substantially 45 with respect to each other to cause both of said pistons to momentarily move in the same direction for a short distance so that when the crankshaft rotates in one direction the charge is delivered in a fully compressed condition to the communicating passage by the pumping piston prior to the time that the working piston is in a position to permit entry of the charge into the combustion chamber and when the crankshaft is rotated in an opposite direction the charge is delivered to the communicating passage by the pumpingpiston at the same instant that the working piston is in a position to permit entry of the charge into the combustion cylinder.

6. A two-cycle engine, comprising two combustion pistons, two pumping pistons, a crankshaft having two laterally spaced crank arms disposed along the axis of the crankshaft at an angle of 180 with respect to each other, and two pairs of connecting rods, the rods forming each pair of connecting rods being laterally disposed in side-by-side relationship with each other along the axis of the crankshaft, the outer ends of each pair of rods respectively connected to a combustion piston and a pumping piston, the inner ends of each pair of rods independently connected to the same crank arm.

7. A two-cycle engine, comprising an engine casing, a first pair of cylinders extending from said casing forming combustion chambers, a second pair of cylinders extending from said casing forming precompression chambers, a piston in each of said cylinders, a crankshaft carried within said casing having two laterally spaced crank arms disposed at an angle of 180 with respect to each other along the axis of the crankshaft, two pairs of connecting rods, the rods forming each pair of connecting rods being laterally disposed in side-by-side relationship with each other along the axis of the crankshaft, the outer ends of each pair of rods respectively connected to a combustion piston and a precompression piston, the inner ends of each pair of rods independently connected in side-by-side relationship to the same crank arm, and a, passage joining all of the cylinders and forming a common communication betweenthe cylinders for the passage of precompressed charges from the second pair of cylinders to the first pair of cylinders.

8. A two-cycle engine, comprising an engine casing, a first pair of cylinders extending from said casing forming combustion chambers, a second pair of cylinders extending from said casing forming precompression chambers, each of said pairs of cylinders extending angularly from the casing in opposite relation to the other pair of cylinders to form an inclusive angle between said pairs of cylinders, a piston in each of said cylinders, a crankshaft carried within the casing havinner ends of each pair of rods independently connected in side-by-side relationship to the same crank arm, whereby the inclusive angle between the pairs of cylinders can be varied and fixed at any angle, and a single passage extending between the first and second pairs of cylinders, said passage forming a common communication between all of the cylinders for the passage of precompressed charges from the second pair of cylinders to the first pair of cylinders.

FREDERICK M. JONES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,154,366 Blume Sept. 21, 1915 1,168,425 Rosenhagen Jan. 18, 1916 FOREIGN PATENTS Number Country Date Great Britain of 1930 

